Device Groups

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In the Oracle Solaris Cluster software, all multihost devices must be under control of the Oracle Solaris Cluster software. The Oracle Solaris Cluster software automatically creates a raw device group for each disk and tape device in the cluster. However, these cluster device groups remain in an offline state until you access them as global devices.

Registration provides the Oracle Solaris Cluster software information about which cluster nodes have a path to specific volume manager disk groups. At this point, the volume manager disk groups become globally accessible within the cluster. If more than one node can write to (master) a device group, the data stored in that device group becomes highly available. The highly available device group can be used to contain cluster file systems.

Note - Device groups are independent of resource groups. One node can master a resource group (representing a group of data service processes). Another node can master the device groups that are being accessed by the data services. However, the best practice is to keep on the same node the device group that stores a particular application's data and the resource group that contains the application's resources (the application daemon). Refer to Relationship Between Resource Groups and Device Groups in Oracle Solaris Cluster Data Services Planning and Administration Guide for more information about the association between device groups and resource groups.

Each cluster node that is physically attached to the multihost disks provides a path to the device group.